HDL & LDL: What You Need to Know About Good and Bad Cholesterol

The word cholesterol may immediately conjure up images of clogged arteries or lab reports circled in red. You may associate cholesterol with negative health outcomes because it frequently gets a bad rap.

But in fact, cholesterol serves an important role in our bodies, such as creating new cells and helping produce hormones.

"Cholesterol is a waxy, fat-like substance that is part of all the cells in our body," says Daniel Hsia, MD, endocrinologist and associate professor at Pennington Biomedical Research Center. "The liver makes all of the cholesterol our body needs."

So while cholesterol may be natural and essential for our bodies to function, it's important to distinguish between the different types of cholesterol: HDL and LDL. They're not created equally, and they don't have the same impacts on your body.

HDL vs. LDL: The Two Types of Cholesterol

There are two main types of cholesterol:

• HDL — high-density lipoprotein or "good" cholesterol
• LDL — low-density lipoprotein or "bad" cholesterol

LDL is known to cause plaque buildup in arteries. This accumulation can eventually lead to interrupted blood flow.

"High LDL cholesterol is linked to progression of atherosclerosis, artery hardening, and progressive narrowing, which causes heart attacks and strokes," says Siddhartha Angadi, PhD, assistant professor of education in the department of kinesiology at the University of Virginia.

On the other hand, HDL can help clean out the built-up cholesterol in the arteries.

"'Good cholesterol,' also known as HDL-C or high-density lipoprotein, is essential for reverse transport of LDL, from the periphery to the liver for disposal," Angadi says.

The two types of cholesterol combined are referred to as total cholesterol.

"Total cholesterol [is] a measure of the total amount of cholesterol in the blood and includes both low-density lipoprotein (LDL) cholesterol and high-density lipoprotein (HDL) cholesterol," explains Hsia.

What Are Ideal Cholesterol Levels?

Ideal cholesterol levels will differ based on many factors. However, it's important to understand your specific health goals and what your cholesterol target should be so that you can understand lab reports and make healthy choices to maintain or change your cholesterol numbers.

"'Normal cholesterol' is a relative term and depends on a person's overall health, age, and sex," says Hsia.

Typically, men and women 20 years and older should target:

• Total cholesterol: from 125 mg/dL to 200 mg/dL
• LDL cholesterol: less than 100 mg/dL
• HDL cholesterol: 40 mg/dL or more for women; 50 mg/dL or more for men

What Happens When LDL Is Too High?

Elevated LDL cholesterol levels can easily can go undetected. In fact, elevated cholesterol is a "silent" problem. The first sign of high cholesterol may be chest pain, breathing issues, or even a heart attack as a result of plaque buildup in the arteries.

"The main reason to be aware of cholesterol levels is to prevent and treat heart disease, also called coronary artery disease or CAD," Hsia says. "CAD happens when the heart is not able to get enough oxygen-rich blood to function well [and] CAD is the leading cause of death in the U.S."

A physical exam and blood work can catch elevated cholesterol levels. There aren't usually warning signs when someone has high levels of "bad" cholesterol, which is why periodic testing is important.

"High cholesterol or abnormal cholesterol levels (dyslipidemia) are clinically silent conditions — there are no symptoms — which is why it is so important to screen for them," Angadi says.

General recommendations state adults should consider being screened every five years and children should first be tested around nine to 11 years old, then tested every five years, explains Hsia.

"When and how often to get your cholesterol tested depends on your age, risk factors, and family history," Hsia says. "Men ages 45 to 65 and women ages 55 to 65 should have cholesterol tested every one to two years."

What Causes High Levels of Cholesterol?

It turns out that your lifestyle has a lot to do with your cholesterol levels, and it is one of the leading factors for high cholesterol. For example, smoking, lack of exercise, and a diet of unhealthy foods can contribute to increased LDL cholesterol levels.

According to Hsia, "Eating a lot of bad fats, such as saturated fat (found in some meats, dairy products, chocolate, baked goods, and deep-fried and processed foods) and trans fat (found in some fried and processed foods) can raise your LDL cholesterol."

The good news is that cholesterol can usually be reduced by changing your lifestyle, including eating healthier and exercising more.

Hsia explains quitting smoking, maintaining a healthy weight, reducing the amount of trans and saturated fats in the diet, and adding more fruits and vegetables, whole grains, and fish, as well as exercising for 150 minutes per week can make a positive difference.

"Dietary cholesterol is only modestly related to cholesterol levels in blood and/or serum," Angadi says. "Components of a healthy diet, especially fiber, can have modest effects on cholesterol levels."

Indeed, fiber can help minimize the amount of cholesterol in the blood by blocking absorption of the fatty substance. "Soluble fiber found in oatmeal or bran reduces absorption of cholesterol into the bloodstream and can modestly reduce LDL levels by about five mg/dL per three grams of soluble fiber," Angadi explains.

The Bottom Line

Oftentimes, lifestyle changes alone can reduce bad cholesterol levels and even help boost good ones, without you needing to take medication.

According to Angadi, "Intensive lifestyle interventions involving daily aerobic exercise and a very-low-fat diet with lots of fiber-rich foods [e.g., 50 to 75 grams of fiber per day] have been shown to lower total cholesterol and 'bad' cholesterol by 25 to 30 percent within just a few weeks, which is comparable to the effects of taking statin drugs to reduce cholesterol."

But for some individuals, lifestyle changes may not be sufficient enough to bring cholesterol levels down to healthy ranges. Medication is an option to get cholesterol levels lowered.

"Statins are very efficacious drugs that lower cholesterol levels and lower the risk of vascular disease related events [e.g. heart attack, stroke, death]," says Angadi.

Related:

• 4 of the Best Foods to Raise Your "Good" Cholesterol, According to Science
• 7 Foods to Skip if You're Trying to Lower Your Cholesterol